This invention relates to a method for the production of dies and molds and more particularly to a spray forming process for the deposition and rapid solidification of atomized molten droplets onto a pattern for manufacturing dies, molds and related tooling.
The recent explosion of interest in rapid prototyping technology is fueled in part by the restructuring of today's marketplace. Successful competition in global markets will require the ability to carry a design concept through the prototype stage to the production stage faster and at lower cost than ever before. The ability to generate plastic and wax models of prototype parts with high dimensional accuracy via selective laser sintering, stereolithography, and other approaches is now a reality. The rapid production of prototype parts from engineered materials (i.e., materials that will actually see service) is a prime goal of industry. Methodologies that can rapidly produce specialized tooling, such as molds and dies, would satisfy this goal when used with conventional manufacturing techniques such as injection molding, blow molding, compression molding, stamping and die casting.
Presently, complex molds, dies and related tooling produced by conventional machining methods are expensive and time consuming to make. Costs can easily exceed hundreds of thousands of dollars and fabrication can require months of effort to produce molds with highly accurate dimensions and tolerances within a few mils or less.
As a consequence of the various disadvantages of conventional machining methods, thermal spray forming processes have been developed for fabricating dies whereby a deposition of a metallic layer on a plaster or metal casting is used to produce the die shell. These conventional processes utilize wire or powder feedstocks and are currently limited to a maximum spray rate of approximately 15 grams per second. Conventional thermal spray processes produce relatively large droplets, generally with mass median diameters in the order of magnitude of 100 .mu.m and with a rather broad distribution of droplet size. Due to the large droplet size, low deposition rate, and heat content associated with conventional spray processes, solidification of the deposited droplets results in relatively poor microstructure, poor mechanical properties, porous deposits and limited material choices. Most high strength metals, including low-carbon, tool, hardfacing and stainless steels have high melting temperatures, thereby limiting the choice of materials used for the pattern or requiring a protective coating on the pattern to protect the pattern from the high temperature metal if conventional spray techniques are to be used. Conventional thermal spray techniques also require feedstocks in the form of metal powders or wires which are relatively expensive and limit material choices.
It is therefore an object of this invention to provide an improved spray forming system for the manufacture of molds, dies and related tooling.
It is another object of this invention to provide a spray forming system that permits the rapid solidification of finely atomized droplets of the molten material sprayed so that patterns made from easy-to-shape materials such as polymer materials, plastics, wax, ceramics or clay may be used.
Additional objects, advantages and novel features of the invention will become apparent to those skilled in the art upon examination of the following and by practice of the invention.